**4.1 Midpoint**

The characterization result of the midpoint analysis as presented in **Table 3** shows that the impact category: global warming is as a result of 0.911 kg of CO2 eq emitted into the air. The consequential effect of global warming is the change in the climatic conditions. Several studies that have been carried out estimated the impact of climatic changes from the production of cement within the range of 0.628 kg CO2 eq 0.920 kg CO2 eq (though their evaluation was with respect to 1ton of cement proceed) per kg of cement produced [10, 24, 35, 48–52]. Ozone formation, Human health and Ozone formation, Terrestrial ecosystem are as a result of 0.00145 kg NOx eq and 0.00147 respectively per kg of OPC. This impact category is measured with NOx emission into the air and also showed it affects human beings. This is one of the main air pollutants which when react with atmospheric air to produce nitrogen dioxide in which its high concentration in human body when inhaled has both direct and indirect effect on humans. It causes death in species and causes health complication on human. 0.000577 kg PM2.5 eq causes Fine particulate matter formation impact for 1 kg of OPC produced. This means that particulate matter with sizes less than 2.5 micrometer is emitted into air. Due to the small sizes of this particle, they have the ability to go through the nasal cavity of human and affect the lungs and other health issues. This value of fine particulate matter in this study is in line with values in literature within the range of 0.00023– 0.0015 kg PM2.5 eq per kg of OPC [36, 52]. The result of terrestrial acidification in this study is 0.0014 SO2 eq and is in line with result of Li et al. (2015) which was in the range 1.144–1.467 kg SO2 eq per kg of OPC [35]. SOx emission is often from the burning of fuel with high Sulfur content and it has high tendency to cause acid rain and other health issues. Emission of 0.00127 kBq Co-60 eq give rise to Ionization radiation. 1 kg of OPC produced emits 0.00127 kilo-Becquerel of Cobalt 60 eq.; this can cause acute radiation, sick burn and even death. **Table 3** also showed that per kg of OPC produced, about 0.455 kg 1,4 DCB eq of different toxicity is emitted in to air and water. 1,4 DCB eq represents 1,4 dichlorobenzene equivalents. This is higher than values found in literature. This might be due to energy sources and fossil fuel mix [48, 53]. High toxicity in the environment (air and waterbodies) have effect on both human and ecosystem. Its health implication is wide-ranging and often times terminal. Pandemic in the aquatic community is often time traced to toxicity. Water consumption during the production of cement is 0.00185 m3: it was found to be comparable with that of Tun et al. and Chen et al. which was within 0.00019-0.00187 m3 [52, 53]. Also 0.0784 kg oil eq of Fossil resources scarcity is expected for every 1 kg of OPC produced. This resonates with the value from the study of [48, 53] with values ranging from 0.07 to 0.234 kg oil eq.; the three impacts categories with high environmental impacts are human health, terrestrial ecotoxicity and Fossil resources scarcity. In order to understand and recognize key factors responsible for these major impact categories, a further contribution analysis was carried out to show that exact substances and process stage contributing to these impacts and their level of contribution.

Global warming impact category results from the emission of 0.911 kg of CO2 eq as seen in **Table 3**. The exact substances that give rise to 0.911 kg of CO2 eq is as represented in **Table 4**. As presented in this table, 97.1% of 0.911 is from actual

emission of CO2 i.e., 0.885 kg of CO2 is emitted per kg of OPC produced. The remaining 0.026 kg of CO2 eq is from the emission of CH4 and N2O. These gases (CO2, CH4 and N2O) are major GHGs, though N2O and CH4 have high capacities to cause global warming: about 25 and 300 respectively, the larger emission of CO2 cause explains why it's the major greenhouse gas that give rise to global warming and consequently climatic changes. The production processes in which these emissions are produced are as presented in **Table 5**. 83.2% of 0.911 kg CO2 eq is from the clinker production phase (both from calcination and burning of fuel) i.e., 0.758 kg of CO2 eq is produced at the clinker production phase and the remaining 0.153 kg of CO2 eq is from various energy sources. A further analysis on co2 emission represented in **Table 6** reveals that 85.6% of the total CO2 emitted during the production of 1 kg of cement (0.885 kg) is emitted at the clinker production phase i.e., 0.75.8 kg of CO2 is emitted at the clinker production stage. Recall that 0.758 kg of CO2 eq is produced at the clinker production phase. This further analysis therefore shows that 0.76 kg of actual CO2 emitted per kg of OPC produced is from clinker production stage. These results are comparable with that of most studies though the result of this study is lower that Stanford's result [48]. In this case more emissions of CO2 are experienced in burning of fuels for the road transportation of clinker. Clinker used for the production of cement in this Brazilian cement plant are imported and on-road transportation being one of the major pollutants and CO2 emitters, higher carbon footprint from this cement plant is inevitable.

Terrestrial ecotoxicity impact category as presented in **Table 3** is as a result of emission of 0.4381 kg of DCB equivalent which is produced into air. **Tables 7** and **8** represent further analysis to know the exact substance and production process respectively contributing to this impact. **Table 7** helps us to know that these impacts are as a result of emissions of heavy metals into the air. Copper has the highest value of 61.5% of all these metals and they all have different effects on both human and the ecosystem having established that whatever affects human affects the ecosystem and vice versa. **Table 8** on the other hand showed the production processes in which the emissions are produced. This shows that the raw material extraction stage (copper production), clinker production and the transportation (break wear emission, lorry) have the highest percentage contributions while others are majorly from energy sources and raw material extraction.

Fossil resource scarcity shows results represent the potential lack of scarcity that can be experienced per kilogram of cement produced. From **Table 3**, 0.0784 kg oil eq becomes scarce per kg OPC produced. This because 43.21% of coal, 43.1% of oil, 13.1% of natural gas are burnt during the production of 1 kg of OPC. This is represented in **Table 9**. These substances are used up at the energy generation phase (in this case are hard coal, petroleum, lignite and natural gas) of the cement production process as represented in **Table 10**.

#### **4.2 Endpoint**

Endpoint analysis categorizes the numerous impact categories into their damage categories based on the effects caused. This is represented in **Table 11**. Further analysis was carried out to show the exact substances production process stage contributing to these damage categories and their level of contribution. Damage to Human health as represented in **Table 11** has a value of 1.22E<sup>6</sup> DALY per kg of OPC produced. As seen in the midpoint analysis, clinker production stage has high contribution; in **Table 13**, clinker production contributes immensely to the damage of human health: 70.1% of damage to human health is from the clinker production process, 24.52% is from energy generation (electricity and fossil fuel) and 1% is from transportation. The substances that are emitted in this production process

### *Life Cycle Assessment of Ordinary Portland Cement (OPC) Using both Problem… DOI: http://dx.doi.org/10.5772/intechopen.98398*

stages that cause this damage is represented in **Table 14**. Again, just as in the midpoint analysis, CO2 emission has high contribution; 67.3% of CO2 emission causes damage to human health, other substances are Nitrogen oxides (8.23%), Sulfur dioxide (12.2%), particulate matter <2.5 μm (9.01%), water (2.5%); each of which have respective implications on human health.

Damage to Ecosystem as recorded in **Table 11** has a value of 3.1E<sup>9</sup> species/yr. per kg of OPC produced. **Tables 15** and **16** show the result of analysis of substance and process responsible for damage to ecosystem respectively. 77.8% of damage to Ecosystem is from the clinker production stage and other production stages are energy generation and transportation. 79.9 of CO2 gas is emitted and thereby cause damage to the ecosystem and other substances such as Nitrogen oxides: 9.48%, Sulfur dioxide 5.6%, methane 2.1% and water 1.2%. Again, this established the fact that whatever will affect ecosystem will affect human health and vice-versa. **Table 11** showed that the potential marginal price increase of Resources per kg of OPC produced is 0.0231 USD (2013). This means that every resource used to produce 1 kg of OPC, poses an increase in the price of those resources by 0.0231 USD (2013). Further analysis to know what these resources are presented in **Table 18** shows that they are crude oil (67.9%), natural gas (16%), hard coal (11.4%) and clay (4.19%). The result of the specification to process represented in **Table 17** shows that about the same percentage amount of the substance is used in the energy generation stage and resource extraction (clay).

The result of the endpoint analysis is comparable with results of literature with CO2 emission and the clinker production stage being the highest contributors [52, 53]. There is variation in the resources of Chen et al. and Tun et al., this is because coal was the major source of fossil fuel for the production of cement.
